1. Field of the Invention
The present invention relates to a semiconductor device and a semiconductor device manufacturing method and, more particularly, a semiconductor device manufacturing method for forming a wiring buried insulating film for burying a wiring formed of a copper film or formed mainly of a copper film, and an inter-wiring layer insulating film that has barrier property to copper.
2. Description of the Prior Art
In recent years, the miniaturization and the reduction in thickness of the pattern are required with the higher integration degree and the higher density of the semiconductor integrated circuit devices. In addition, since the higher speed of the data transfer rate is also required.
Therefore, the insulating film having the low dielectric constant (referred to as a xe2x80x9clow dielectric constant insulating filmxe2x80x9d hereinafter) and the small RC delay is employed. As such insulating film, there are the SiOF film having the relative dielectric constant 3.5 to 3.8, the porous SiO2 film having the relative dielectric constant 3.0 to 3.1, etc., for example.
In the meanwhile, the wiring material is being changed from the conventional aluminum (Al) to the wiring formed of the copper (Cu) film having a low electric resistance or formed mainly of the copper film (referred to as a xe2x80x9ccopper wiringxe2x80x9d hereinafter).
Therefore, in order to manufacture the semiconductor device having the multi-layered copper wiring, the low dielectric constant insulating film is formed as the interlayer insulating film on the copper wiring in the prior art. In this case, since normally the copper is ready to diffuse from the copper wiring into the low dielectric constant insulating film, the leakage current between upper and lower wirings is increased. Accordingly, in order to prevent the diffusion of the copper element into the low dielectric constant insulating film, the barrier insulating film containing Si and N or Si and C is often interposed between the copper wiring and the low dielectric constant insulating film.
However, the insulating film containing Si and N has the high relative dielectric constant. Therefore, even if such insulating film of the thinner film thickness is employed as the barrier insulating film, the dielectric constant of the overall interlayer insulating film is increased.
Also, the relative dielectric constant of the barrier insulating film containing Si and C is relatively low such as about 5 rather than the barrier insulating film containing Si and N. But such barrier insulating film containing Si and C cannot sufficiently suppress the increase in the leakage current. In this case, in order to suppress sufficiently the leakage current, further the oxygen must be introduced into the barrier insulating film containing Si and C.
The leakage current can be reduced to a sufficient level by doing so. However, the new problem is caused such that the surface of the copper wiring is oxidized and thus the barrier insulating film and the low dielectric constant insulating film are easily peeled off.
It is an object of the present invention to provide a semiconductor device and a semiconductor device manufacturing method capable of preventing peeling-off of an insulating film for covering a wiring made of only or mainly a copper film and achieving a low dielectric constant of an interlayer insulating film between wirings made of copper film etc. while maintaining a high barrier characteristic to a copper and a small leakage current, like the silicon nitride film, when an inter-wiring layer insulating film into which a connecting conductor is buried and a wiring-buried insulating film into which the copper wiring is buried are formed.
Advantages that can be achieved by the configuration of the present invention will be explained hereunder.
The PE-CVD TMS SiO2 film according to the present invention has a peak of an absorption intensity of an infrared rays in a range of a wave number 2270 to 2350 cmxe2x88x921, a film density in a range of 2.25 to 2.40 g/cm3, and a relative dielectric constant in a range of 3.3 to 4.3.
According to the experiment by the inventor of the present invention, the PE-CVD TMS SiO2 film having the aforementioned characteristics has a high mechanical strength, is dense, has a high water resistance, and has a small content of moisture similarly to a silicon nitride film, and is a lower relative dielectric constant than the silicon nitride.
The semiconductor device of the present invention has a protection layer covering a wiring made only or mainly of a copper film, and the protection layer is formed of the PE-CVD TMS SiO2 film having the aforementioned characteristics. Accordingly, since the protection layer is dense similarly to a silicon nitride, it can prevent the copper from diffusing from the wiring to a periphery thereof.
Further, an inter-wiring layer insulating film having the aforementioned characteristics is interposed between the lower wiring and the upper wiring. Therefore, the inter-wiring layer insulating film can prevent the copper from diffusing from the wiring to a periphery thereof, while the semiconductor device maintains a lower dielectric constant.
Moreover, the semiconductor device has a main insulating film, protection layers covering it in both a lower surface and an upper surface. In other words, the protection layers having the aforementioned characteristics are interposed both between the lower wiring and the main insulating film and between the upper wiring and the main insulating film, respectively. Therefore, the protection layers can prevent the copper from diffusing from the wirings to the main insulating film.
Further, employing a porous insulating film or a coating insulating film having a lower dielectric constant as the main insulating film results in preventing the copper from diffusing from the wirings to the main insulating film, while maintaining a lower dielectric constant.
The insulating film is formed by plasmanizing the film forming gas, that consists of any one selected from the group consisting of the alkoxy compound having Sixe2x80x94H bonds and the siloxane having Sixe2x80x94H bonds and any one oxygen-containing gas selected from the group consisting of O2, N2O, NO2, CO, CO2, and H2O, to react.
According to the experiment, it is found that the silicon-containing insulating film, that formed by plasmanizing the film forming gas that consists of any one selected from the group consisting of the alkoxy compound having Sixe2x80x94H bonds and the siloxane having Sixe2x80x94H bonds and any one oxygen-containing gas selected from the group consisting of O2, N2O, NO2, CO, CO2, and H2O to react, is dense, is excellent in the water resistance, and has the small amount of contained moisture in the film, that are equivalent to the silicon nitride film, and has the smaller relative dielectric constant than the silicon nitride film.
Therefore, in the method of manufacturing the semiconductor device in which the inter-wiring layer insulating film is put between the lower wiring-buried insulating film into which the lower wiring formed of the copper film or formed mainly of the copper film is buried and the upper wiring-buried insulating film into which the upper wiring formed of the copper film or formed mainly of the copper film is buried, the inter-wiring layer insulating film is formed by the above film forming condition. In other words, since the inter-wiring layer insulating film is interposed between the lower wiring and upper wiring, the diffusion of the copper from the lower wiring and the upper wiring can be prevented without the barrier insulating film and also the semiconductor can achieve the lower dielectric constant in the overall insulating film between the wirings.
Also, the main insulating films and the protection layers made of the silicon-containing film of the present invention are laminated alternatively in this order from a bottom to form two or more inter-wiring layer insulating films and two or more wiring buried insulating films alternatively in this order from a bottom. The inter-wiring layer insulating films and the wiring buried insulating films include at least the main insulating film and the protection layer, respectively. Then via holes and wiring recesses are formed alternatively in the inter-wiring layer insulating films and the wiring-buried insulating films, and then a metal consisting only or mainly of a copper film is buried in the via holes and the wiring recesses to form the, connecting conductor and the wiring connecting to the connecting conductor. In this case, the method of forming the connecting conductor and the copper wiring by laminating the inter-wiring layer insulating films and the wiring-buried insulating films, then forming the via hole and the wiring recess therein, and then filling the copper film or the like in the via hole and the wiring recess is referred to as the so-called dual damascene method.
According to the above structure, since the protection layer is interposed between the wiring made of the copper film or the like and the main insulating film, the diffusion of the copper from the copper wirings into the main insulating film can be prevented.
Also, if the main insulating film is formed of the SiOF film, for example, the diffusion of the fluorine (F) element into the peripheral portions can be prevented by the protection layer made of the silicon-containing insulating film of the present invention.
In addition, since the protection layer is formed of not the silicon nitride film but the insulating film having a low relative dielectric constant, the dielectric constant can be reduced in the overall insulating film between the wirings.
Further, since the protection layer made of the silicon-containing insulating film of the present invention is formed to cover the lower wiring, the diffusion of the copper into the peripheral portions can be prevented.
Furthermore, since the silicon-containing insulating film of the present invention has essentially the small leakage current like the silicon nitride film, the introduction of the oxygen is not needed to reduce the leakage current, unlike the insulating film containing Si and C. Although the protection layer and the inter-wiring layer insulating film that contact to the wiring made of copper or the like are ready to peel off if the surface of the wiring made of copper or the like is oxidized by the introduced oxygen or the oxygen introducing process, there is no possibility of that peeling-off in the present invention.
Moreover, if the main insulating film is formed of the coating insulating film, the peeling-off of the film can be prevented and also the discharge of the moisture from the coating insulating film into the peripheral portions can be prevented more completely since the protection layer of the present invention has the good adhesiveness to the coating insulating film.
Besides, the semiconductor is formed of, from the bottom, the inter-wiring layer insulating film and the wiring-buried insulating film formed by laminating sequentially two or more sets of the insulating films and the protection layers made of the silicon-containing insulating film according to the present invention, and then the via holes and the wiring recesses connected to the via holes are formed alternatively to pass through the inter-wiring layer insulating film and the wiring-buried insulating film such that their opening areas are expanded sequentially from the lower side respectively. In other words, the protection layer is exposed from the insulating film that is to be etched, or acts as the underlying film of the insulating film that is to be etched when the insulating film is selectively etched. In this case, since the protection layer of the present invention is dense, such film can effectively function as the mask or such film can effectively function as the stopper to prevent the excessive etching of the insulating film formed under the protection layer.